Polymer capacitors that mitigate anomalous charging current

ABSTRACT

Many electronic devices may employ electrolytic polymer capacitors in their power supplies for noise filtering, decoupling/bypassing, frequency conversion and DC-DC and AC-DC conversion. However, some polymer capacitors exhibit an anomalous charging current phenomenon, which may prevent proper charging and cause failure in power circuits of the electronic devices. Disclosed herein are polymer capacitors that have a wide band gap material layer between an insulator/dielectric and a polymer cathode, a charge depletion region in the insulator/dielectric, or both, that may mitigate the anomalous charging current.

BACKGROUND

The present disclosure relates generally to capacitors and, morespecifically, to polymer capacitors and anomalous charging current,particularly under fast slew rate of voltage during application.

This section is intended to introduce the reader to various aspects ofart that may be related to various aspects of the present disclosure,which are described and/or claimed below. This discussion is believed tobe helpful in providing the reader with background information tofacilitate a better understanding of the various aspects of the presentdisclosure. Accordingly, it should be understood that these statementsare to be read in this light, and not as admissions of prior art.

An electronic device, such as a laptop, tablet, or cell phone, may havea power supply which converts current from a charging cable or a batteryto a desired voltage and frequency to power various components of theelectrical device. The power supply may use one or more polymercapacitors to power on the electrical device and supply power to theelectrical device to enable it to function properly. Advantageously,polymer capacitors are compact in size and exhibit high reliability andlow equivalent series resistance (ESR), which makes them suitable forconsumer electronics. However, in some cases, the polymer capacitorsexhibit anomalous charging current, which may result in unpredictablecharging or powering of electronic devices, and even causing theelectronic devices to fail to power on.

SUMMARY

A summary of certain embodiments disclosed herein is set forth below. Itshould be understood that these aspects are presented merely to providethe reader with a brief summary of these certain embodiments and thatthese aspects are not intended to limit the scope of this disclosure.Indeed, this disclosure may encompass a variety of aspects that may notbe set forth below.

In one embodiment, a capacitor has a conductive anode, a dielectriclayer deposited on the conductive anode, a wide electronic band gaplayer deposited on the dielectric, and a semiconductive cathode disposedon the wide electronic band gap layer.

In another embodiment, a capacitor has a conductive anode, a dielectriclayer with a charge depletion region, and a semiconductive cathodedeposited on the dielectric layer.

In another embodiment, a capacitor has a conductive anode, a dielectriclayer with a charge depletion region, a wide electronic band gap layerdeposited on top of the dielectric, and a semiconductive cathode.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of this disclosure may be better understood upon readingthe following detailed description and upon reference to the drawings inwhich:

FIG. 1 is a block diagram of an electrical device that having thepolymer capacitors described herein, in accordance with an embodiment ofthe present disclosure;

FIG. 2 is a perspective view of a notebook computer employing thepolymer capacitors described herein, in accordance with an embodiment ofthe present disclosure;

FIG. 3 is a front view of a hand-held device employing the polymercapacitors described herein, in accordance with an embodiment of thepresent disclosure;

FIG. 4 is a front view of portable tablet computer employing the polymercapacitors described herein, in accordance with an embodiment of thepresent disclosure;

FIG. 5 is a front view of a desktop computer employing the polymercapacitors described herein, in accordance with an embodiment of thepresent disclosure;

FIG. 6 is a front and side view of a wearable electrical deviceemploying the polymer capacitors described herein, in accordance with anembodiment of the present disclosure;

FIG. 7 is a circuit diagram of a buck circuit having a polymer capacitordescribed herein, in accordance with an embodiment of the presentdisclosure;

FIG. 8 is a circuit diagram of a boost circuit having a polymercapacitor described herein, in accordance with an embodiment of thepresent disclosure;

FIG. 9A is a graph of a change of current and voltage with time in anideal polymer capacitor circuit;

FIG. 9B is a graph of a change of current and voltage with time in apolymer capacitor circuit exhibiting anomalous charging currentbehavior;

FIG. 10 is a perspective diagram of a polymer capacitor with a wide bandgap material layer between an insulator/dielectric and a semiconductivecathode (e.g., a polymer cathode), in accordance with an embodiment ofthe present disclosure;

FIG. 11 is a flowchart of a method for producing the polymer capacitorof FIG. 10 , in accordance with an embodiment of the present disclosure;

FIG. 12 is a perspective diagram of a polymer capacitor with chargedepletion region in the insulator/dielectric, in accordance with anembodiment of the present disclosure;

FIG. 13 is a flowchart of a method for producing the polymer capacitorof FIG. 12 , in accordance with an embodiment of the present disclosure;

FIG. 14 is a perspective diagram of a polymer capacitor with the chargedepletion region in the insulator/dielectric and the wide band gapmaterial layer between the insulator/dielectric and the semiconductivecathode, in accordance with an embodiment of the present disclosure;

FIG. 15 is a flowchart of a method for producing the polymer capacitorof FIG. 14 , in accordance with an embodiment of the present disclosure;

FIG. 16 is a flowchart for producing a tantalum-based polymer capacitorwith a wide band gap silicon dioxide (SiO₂) layer, in accordance with anembodiment of the present disclosure;

FIG. 17 is a flowchart of a method for producing a tantalum-basedpolymer capacitor with charge depletion region in theinsulator/dielectric introduced by electrochemical deposition, inaccordance with an embodiment of the present disclosure;

FIG. 18 is a flowchart of a method for producing a tantalum-basedpolymer capacitor with charge depletion region in theinsulator/dielectric introduced by ion implantation and electrochemicaldeposition, in accordance with an embodiment of the present disclosure;

FIG. 19 is a flowchart of a method for producing a tantalum-basedpolymer capacitor with charge depletion region in theinsulator/dielectric and a wide band gap lanthanum(III) oxide (La₂O₃)layer, in accordance with an embodiment of the present disclosure; and

FIG. 20 is a flowchart of a method for producing a niobiummonoxide-based polymer capacitor with charge depletion region in theinsulator/dielectric and a wide band gap hafnium oxide (HfO₂) layer, inaccordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

One or more specific embodiments will be described below. In an effortto provide a concise description of these embodiments, not all featuresof an actual implementation are described in the specification. Itshould be appreciated that in the development of any such actualimplementation, as in any engineering or design project, numerousimplementation-specific decisions must be made to achieve thedevelopers’ specific goals, such as compliance with system-related andbusiness-related constraints, which may vary from one implementation toanother. Moreover, it should be appreciated that such a developmenteffort might be complex and time consuming, but would nevertheless be aroutine undertaking of design, fabrication, and manufacture for those ofordinary skill having the benefit of this disclosure.

Electronic devices may employ electrolytic polymer capacitors (from nowon referred simply as polymer capacitors) in their power supplies fornoise filtering, decoupling/bypassing, frequency conversion and directcurrent to direct current (DC-DC) and alternating current to directcurrent (AC-DC) conversion. The polymer capacitors have advantageouscharacteristics such as high capacitance, low equivalent seriesresistance, volumetric efficiency, stability over long servicelifetimes, and long-term reliability under harsh operating conditions.Due to these superior characteristics, polymer capacitors are widelyused in consumer electronics as well as high-reliability applicationsincluding automotive, defense, and aerospace.

As further discussed below, polymer capacitors may include an anode(e.g., a positively charged plate of the capacitor) made of a conductivematerial and a cathode (e.g., a negatively changed plate of thecapacitor) made of a semiconductive material (material with aconductivity of a semiconductor), separated by an insulator/dielectriclayer (e.g., which may be at least partially composed of metal oxide).The conductive (e.g., having a conductivity of an electrical conductor)anode of the polymer capacitor may include a metal, such as tantalum(Ta), niobium (Nb), and/or aluminum (Al), and/or a compound withmetallic conductivity, such as niobium monoxide (NbO). Thesemiconductive (e.g., having a conductivity of a semiconductor) cathodeof the polymer capacitor may be at least partially formed by conductingpolymers (e.g., polymers that are able to conduct electricity), such aspoly (3,4-ethylenedioxythiophene) (PEDOT), poly(3,4-ethylenedioxythiophene) and polystyrene sulfonate (PSS) slurry(PEDOT:PSS), or polypyrrole (PPy). Meanwhile, the insulator/dielectriclayer may be at least partially formed by a metal oxide formed from theconductive anode material, such as tantalum pentoxide (Ta₂O₅), niobiumpentoxide (Nb₂O₅), and/or aluminum(III) oxide (Al₂O₃).

As mentioned above, in some cases, polymer capacitors may exhibitanomalous charging current phenomenon, resulting in unpredictablecharging or powering behavior of electronic devices, and even causingthe electronic devices to fail to power on. In an ideal scenario,current in a circuit having a voltage source and a capacitor may beproportional to a rate of change in voltage across the capacitor.However, in some polymer capacitors, the current (e.g., an anomalous,abnormal, or atypical charging current) may exceed the valueproportional to the rate of change in voltage, for example, when thevoltage change rate is fast (around a few volts per millisecond) andvoltage applied has reached a certain threshold value. One consequenceof this anomalous charging current is that polymer capacitors may outputunpredictable current waveforms. Moreover, some devices may not supplyenough power to sustain the high current, which may lead to devicemalfunction. In some embodiments, the anomalous charging current may beassociated with an absence of moisture within the polymer cathode, andmay be particularly pronounced in polymer capacitors that were chargedimmediately after undergoing surface-mounting processes (e.g., mountingonto a surface of a circuit board) without having sufficient time tostabilize.

In some cases, the anomalous charging current in polymer capacitors maybe attributed to two types of phenomena: conduction mechanisms at aninterface between the insulator/dielectric and the semiconductivecathode of a capacitor, and bulk-limited conduction mechanisms in theinsulator/dielectric layer. The conduction mechanisms at the interfacemay include thermionic emission (e.g., the Schottky effect), fieldemission, and thermionic-field emission. During thermionic emission,electrons in the semiconductive cathode may obtain enough thermal energyto overcome the energy barrier at the interface and move into thedielectric. During field emission, the interface effects can includequantum phenomena, such as direct and Fowler-Nordheim tunneling ofelectrons across the insulator/dielectric energy barrier, which mayhappen if the insulator/dielectric layer is thin. Under the directtunneling conditions, an electron tunnels through the wholeinsulator/dielectric energy barrier, whereas under the Fowler-Nordheimconditions, the electron tunnels through a part of the barrier to aconduction band of the insulator. From there, the electron may flow tothe conductive anode. During thermionic-field emission, thermally-exitedelectrons may find their way to the locations where the triangularenergy barrier is relatively narrow, thus making tunneling easier. Thebulk-limited conduction in the insulator/dielectric layer may arise dueto ionic conduction under electric field associated with point latticedefects (e.g., vacancy defects), such as oxygen and metal vacancies, inmetal oxide introduced during the formation of the insulator/dielectriclayer. In parallel, assisted by the electric field, electrons in theinsulator/dielectric may be promoted into the conduction band by thermalexcitations. The electrons may move through a crystal in the conductionband for a brief amount of time, before relaxing into an energy “trap.”Vacancy defects may act as energy “traps,” leading to the conduction ofelectrons through the bulk of the insulator/dielectric. These phenomenaare known as Poole-Frenkel emission and hopping. Any or all of theaforementioned conduction mechanisms may contribute to the anomalouscharging current in the polymer capacitors.

While attempts may be made to address the anomalous charging current byin-line testing at the manufacturing site to screen out capacitors withsevere anomalous charging current behavior and/or increasing a thicknessof the insulator/dielectric layer at the expense of the capacitor’sability to store charge, neither of these approaches have been effectiveand satisfactory, particularly for mass production.

Embodiments described herein include polymer capacitors that may provideprotection from and/or mitigate the anomalous charging currentphenomenon. To that end, the polymer capacitors may include a wide bandgap material layer between the semiconductive polymer cathode and theinsulator/dielectric, and/or a charge depletion region inside theinsulator/dielectric introduced through doping impurities. That is,certain embodiments may include polymer capacitors with the wide bandgap material layer between the semiconductive polymer cathode and theinsulator/dielectric. Additional or alternative embodiments may includepolymer capacitors with the charge depletion region inside theinsulator/dielectric layer introduced by doping impurities. Furtherstill, certain embodiments may include polymer capacitors with both thewide band gap material layer between and a charge depletion regioninside the insulator/dielectric introduced through doping impurity. Suchcapacitors may, along with appropriate system design, lead to improvedreliability of the electronic devices, which may operate in a morefault-tolerant manner.

With the foregoing in mind, a general description of suitable electronicdevices that may employ polymer capacitors in their circuitry will beprovided below. Turning first to FIG. 1 , an electronic device 10according to an embodiment of the present disclosure may include, amongother things, one or more processor(s) 12, memory 14, nonvolatilestorage 16, a display 18, input structures 22, an input/output (I/O)interface 24, a network interface 26, and a power source 28. The variousfunctional blocks shown in FIG. 1 may include hardware elements(including circuitry), software elements (including computer code storedon a computer-readable medium) or a combination of both hardware andsoftware elements. It should be noted that FIG. 1 is merely one exampleof a particular implementation and is intended to illustrate the typesof components that may be present in electronic device 10.

By way of example, the electronic device 10 may represent a blockdiagram of the notebook computer depicted in FIG. 2 , the handhelddevice depicted in FIG. 3 , the handheld device depicted in FIG. 4 , thedesktop computer depicted in FIG. 5 , the wearable electronic devicedepicted in FIG. 6 , or similar devices. It should be noted that theprocessor(s) 12 and other related items in FIG. 1 may be generallyreferred to herein as “data processing circuitry.” Such data processingcircuitry may be embodied wholly or in part as software, firmware,hardware, or any combination thereof. Furthermore, the data processingcircuitry may be a single contained processing module or may beincorporated wholly or partially within any of the other elements withinthe electronic device 10.

In the electronic device 10 of FIG. 1 , the processor(s) 12 may beoperably coupled with the memory 14 and the nonvolatile storage 16 toperform various algorithms. Such programs or instructions executed bythe processor(s) 12 may be stored in any suitable article of manufacturethat includes one or more tangible, computer-readable media at leastcollectively storing the instructions or routines, such as the memory 14and the nonvolatile storage 16. The memory 14 and the nonvolatilestorage 16 may include any suitable articles of manufacture for storingdata and executable instructions, such as random-access memory,read-only memory, rewritable flash memory, hard drives, and opticaldiscs. In addition, programs (e.g., an operating system) encoded on sucha computer program product may also include instructions that may beexecuted by the processor(s) 12 to enable the electronic device 10 toprovide various functionalities.

In certain embodiments, the display 18 may be a liquid crystal display(LCD), which may allow users to view images generated on the electronicdevice 10. In some embodiments, the display 18 may include a touchscreen, which may allow users to interact with a user interface of theelectronic device 10. Furthermore, it should be appreciated that, insome embodiments, the display 18 may include one or more organic lightemitting diode (OLED) displays, or some combination of LCD panels andOLED panels.

The input structures 22 of the electronic device 10 may enable a user tointeract with the electronic device 10 (e.g., pressing a button toincrease or decrease a volume level). The I/O interface 24 may enableelectronic device 10 to interface with various other electronic devices,as may the network interface 26. The network interface 26 may include,for example, one or more interfaces for a personal area network (PAN),such as a Bluetooth network, for a local area network (LAN) or wirelesslocal area network (WLAN), such as an 802.11x Wi-Fi network, and/or fora wide area network (WAN), such as a 3rd generation (3G) cellularnetwork, 4th generation (4G) cellular network, long term evolution (LTE)cellular network, or long term evolution license assisted access(LTE-LAA) cellular network. The network interface 26 may also includeone or more interfaces for, for example, broadband fixed wireless accessnetworks (WiMAX), mobile broadband Wireless networks (mobile WiMAX),asynchronous digital subscriber lines (e.g., ADSL, VDSL), digital videobroadcasting-terrestrial (DVB-T) and its extension DVB Handheld (DVB-H),ultra-Wideband (UWB), alternating current (AC) power lines, and soforth. Network interfaces 26 such as the one described above may benefitfrom the use of tuning circuitry, impedance matching circuitry and/ornoise filtering circuits that may include polymer capacitors such as theones described herein. As further illustrated, the electronic device 10may include a power source 28. The power source 28 may include anysuitable source of power, such as a rechargeable lithium polymer(Li-poly) battery and/or an alternating current (AC) power converter.

In certain embodiments, the electronic device 10 may take the form of acomputer, a portable electronic device, a wearable electronic device, orother type of electronic device. Such computers may include computersthat are generally portable (such as laptop, notebook, and tabletcomputers) as well as computers that are generally used in one place(such as conventional desktop computers, workstations, and/or servers).In certain embodiments, the electronic device 10 in the form of acomputer may be a model of a MacBook®, MacBook® Pro, MacBook Air®,iMac®, Mac® mini, or Mac Pro® available from Apple Inc. By way ofexample, the electronic device 10, taking the form of a notebookcomputer 10A, is illustrated in FIG. 2 in accordance with one embodimentof the present disclosure. The depicted computer 10A may include ahousing or enclosure 36, a display 18, input structures 22, and ports ofan I/O interface 24. In one embodiment, the input structures 22 (such asa keyboard and/or touchpad) may be used to interact with the computer10A, such as to start, control, or operate a GUI or applications runningon computer 10A. For example, a keyboard and/or touchpad may allow auser to navigate a user interface or application interface displayed ondisplay 18.

FIG. 3 depicts a front view of a handheld device 10B, which representsone embodiment of the electronic device 10. The handheld device 10B mayrepresent, for example, a portable phone, a media player, a personaldata organizer, a handheld game platform, or any combination of suchdevices. By way of example, the handheld device 10B may be a model of aniPod® or iPhone® available from Apple Inc. of Cupertino, California. Thehandheld device 10B may include an enclosure 36 to protect interiorcomponents from physical damage and to shield them from electromagneticinterference. The enclosure 36 may surround the display 18. The I/Ointerfaces 24 may open through the enclosure 36 and may include, forexample, an I/O port for a hard-wired connection for charging and/orcontent manipulation using a standard connector and protocol, such asthe Lightning connector provided by Apple Inc., a universal serial bus(USB), or other similar connector and protocol.

User input structures 22, in combination with the display 18, may allowa user to control the handheld device 10B. For example, the inputstructures 22 may activate or deactivate the handheld device 10B,navigate user interface to a home screen, a user-configurableapplication screen, and/or activate a voice-recognition feature of thehandheld device 10B. Other input structures 22 may provide volumecontrol, or may toggle between vibrate and ring modes. The inputstructures 22 may also include a microphone may obtain a user’s voicefor various voice-related features, and a speaker may enable audioplayback and/or certain phone capabilities. The input structures 22 mayalso include a headphone input may provide a connection to externalspeakers and/or headphones.

FIG. 4 depicts a front view of another handheld device 10C, whichrepresents another embodiment of the electronic device 10. The handhelddevice 10C may represent, for example, a tablet computer, or one ofvarious portable computing devices. By way of example, the handhelddevice 10C may be a tablet-sized embodiment of the electronic device 10,which may be, for example, a model of an iPad® available from Apple Inc.of Cupertino, California.

Turning to FIG. 5 , a computer 10D may represent another embodiment ofthe electronic device 10 of FIG. 1 . The computer 10D may be anycomputer, such as a desktop computer, a server, or a notebook computer,but may also be a standalone media player or video gaming machine. Byway of example, the computer 10D may be an iMac®, a MacBook®, or othersimilar device by Apple Inc. It should be noted that the computer 10Dmay also represent a personal computer (PC) by another manufacturer. Asimilar enclosure 36 may be provided to protect and enclose internalcomponents of the computer 10D such as the display 18. In certainembodiments, a user of the computer 10D may interact with the computer10D using various peripheral input devices, such as the keyboard 22A ormouse 22B (e.g., input structures 22), which may connect to the computer10D.

Similarly, FIG. 6 depicts a wearable electronic device 10E representinganother embodiment of the electronic device 10 of FIG. 1 that may beconfigured to operate using the techniques described herein. By way ofexample, the wearable electronic device 10E, which may include awristband 43, may be an Apple Watch® by Apple, Inc. However, in otherembodiments, the wearable electronic device 10E may include any wearableelectronic device such as, for example, a wearable exercise monitoringdevice (e.g., pedometer, accelerometer, heart rate monitor), or otherdevice by another manufacturer. The display 18 of the wearableelectronic device 10E may include a touch screen display 18 (e.g., LCD,OLED display, active-matrix organic light emitting diode (AMOLED)display, and so forth), as well as input structures 22, which may allowusers to interact with a user interface of the wearable electronicdevice 10E.

The electronic device 10 described above may include one or more polymercapacitors in its power source 28 (e.g., power supply circuitry). Forexample, the power source 28 may include a buck converter having one ormore polymer capacitors as disclosed herein. The buck converter is adirect current-direct current (DC-DC) converter, which may reducevoltage from an input to an output. FIG. 7 is a circuit diagram of abuck converter 50 (e.g., a buck converter circuit), in accordance withan embodiment of the present disclosure. As illustrated, the buckconverter 50 has a DC voltage source 52 (e.g., a battery), a switch 54(e.g., a metal-oxide-semiconductor field-effect transistor (MOSFET)), adiode 56, an inductor 58, the disclosed polymer capacitor 60, and aload/resistor 62. In particular, the DC voltage source 52, the diode 56,the polymer capacitor 60, and the load/resistor 62. When switch 54 isclosed (e.g., acting as a short circuit and enabling current to passthrough), the current will flow from the battery 52 to the remainder ofthe buck converter 50. Initially, the inductor 58 may oppose the suddencurrent increase, storing energy in its magnetic field and reducing thevoltage across the load/resistor 62. Eventually, however, the magneticfield may stabilize, causing the inductor 58 to conduct current. Thus,while the switch 54 is closed, the voltage across the load/resistor 62approaches the input voltage and the current charges the capacitor 60.Meanwhile, the diode 56 is reversed-biased, blocking current frompassing through it. When the switch 54 is open (acting as an opencircuit and preventing current from passing through), the DC voltagesource 52 is cut off from the remainder of the buck converter 50 by theswitch 54 and the now forward-biased diode 56. The current flowingthrough the inductor 58 may begin to decrease, reducing the inductor’s58 magnetic field, and changing the inductor’s 58 polarity and making ita new source of current. During this time, the capacitor 60 maydischarge, assisting the inductor 58 in supplying current to theload/resistor 62, and thereby ensuring a stable voltage drop until theswitch 54 closes bringing the voltage across the load/resistor 62 backup.

A boost converter is another example of an electrical circuit that mayinclude one or more polymer capacitors 60 as disclosed herein and thatmay be found in the power source 28 of the electronic device 10. Likethe buck converter 50, the boost converter 64 is a DC-DC converter.However, instead of reducing the voltage from input to output, the boostconverter increases the voltage. FIG. 8 is a circuit diagram of a boostconverter 64 (e.g., a boost converter circuit), according to anembodiment of the present disclosure. The boost converter 64 has similarelectrical components as the buck converter 50, though the componentsmay be arranged differently. The boost converter 64 may include the DCvoltage source 52 (e.g., a battery), the switch 54 (e.g., a MOSFET), thediode 56, the inductor 58, the polymer capacitor 60, and theload/resistor 62. When the switch 54 is closed, current may flow throughthe inductor 58 and the switch 54. During this time, the inductor 58 mayaccumulate energy. When the switch 54 opens (turns off), the inductor 58may release the stored energy by pushing a current through the diode 56charging the polymer capacitor 60. When the switch 54 closes again, thepolymer capacitor 60 may supply voltage and energy to the load/resistor62. During this time, the diode 56 may prevent the polymer capacitor 60from discharging through the switch 54. The switch 54 may open again(e.g., within a threshold period of time) to prevent the polymercapacitor 60 from excessive discharge. Thus, repeating the cycle ofclosing and opening the switch 54 may further build up output voltage inthe boost converter 64.

Polymer capacitors (such as the polymer capacitor 60) may be used in theDC-DC power circuits described above to bulk or boost voltage per loadrequirement. Such circuits may rely on ideal or near ideal charging ofthe polymer capacitor 60. Hypothetically, a capacitor 60 may demonstratestable current as voltage across the capacitor 60 linearly rises, asshown in FIG. 9A below. If anomalous charging of the polymer capacitor60 happens, as shown in FIG. 9B below, the buck 50 and boost 64converters may be incapable of regulating voltage in a power circuit asdesigned.

FIG. 9A is a graph 70A of a change in current 72 and voltage 74 withtime in an ideal polymer capacitor circuit. In a circuit with an idealpolymer capacitor and a voltage source, the current-voltage relation isgoverned by the formula shown in Equation 1 below:

$I = C \times \frac{dV}{dt}$

where I is the current 72 in the circuit, C is the capacitance of thepolymer capacitor, and V is the voltage 74 across the polymer capacitor.Therefore, the current 72 is proportional to the rate of change involtage 74 with respect to time. If voltage 74 across the capacitorincreases linearly, then the current 72 will be constant, as shown onthe graph 70A. Such a current-voltage relationship may lead to properoperation of the power circuits and may be found in the polymercapacitor where the interface-limited conduction mechanisms (e.g.,thermionic emission, thermionic-field emission, field emission, directtunneling, Fowler-Nordheim tunneling) and the bulk-limited conductionmechanisms (e.g., ionic conduction, Poole-Frenkel emission and hopping)are absent, reduced, or mitigated.

FIG. 9B is a graph 70B of a change in current 72 and voltage 74 withtime in a polymer capacitor circuit exhibiting the anomalous chargingcurrent phenomenon. Due to the aforementioned bulk-limited conductionmechanisms and interface-limited conduction mechanisms, the current 72in the polymer capacitor circuit may not accurately follow the formulaor relationship shown in Equation 1 above, particularly when the changeof voltage is fast. Instead, when a medium-to-high (but lower than thevoltage rating of the capacitor) voltage 74 is applied by the voltagesource, the current 72 may rise much faster than the rate change involtage 74 with time, resulting in anomalous charging current behavior76 (e.g., a current spike or sharp increase of current), and higherpower demand. As mentioned, such anomalous charging current behavior maycause polymer capacitors to output unpredictable current waveforms,prevent the polymer capacitors from charging properly, and/or compromisethe circuits that incorporate such polymer capacitors.

However, the disclosed polymer capacitors 60 may mitigate the anomalouscharging current phenomenon. A first embodiment may include a wide bandgap material layer between the insulator/dielectric and thesemiconductive cathode in the polymer capacitor 60. FIG. 10 shows aperspective diagram of a polymer capacitor 60A with a wide band gapmaterial layer 86 between the insulator/dielectric 84 and thesemiconductive cathode 88, in accordance with an embodiment. Band gapmay refer to a minimum energy that a valence electron (e.g., an electronthat is bound to an atom and cannot contribute to electricalconductivity) needs to gain to become a conduction electron (e.g., anelectron that is not bound to an atom and moves within a solidcontributing to electrical conductivity). The valence electron is saidto be in a valence band (e.g., a group of energy levels that boundelectrons may have) while the conduction electron is said to be in aconduction band (e.g., a group of energy levels that unbound electronsmay have). In other words, the band gap may refer to a differencebetween the lowest energy in the conduction band and highest energy inthe valence band. In molecular materials such as conducting polymers,band gap may refer to an energy difference between an electron in alowest unoccupied molecular orbital (LUMO) and an electron in a highestoccupied molecular orbital (HOMO). HOMO and LUMO in molecular materials(e.g., conducting polymers) may be analogous to valence and conductionbands in solids (e.g., Ta, Nb, NbO, Al, Ta₂O₅, Nb₂O₅, Al₂O₃, and so on).Thus, a wide band gap material may include a material where an energydifference between the lowest energy in the conduction band and thehighest energy in the valence band is greater than that of theinsulator/dielectric 84. A wide band gap material may also include amaterial where an energy difference between LUMO and HOMO (e.g., used topromote an electron from the LUMO to the HOMO of the wide band gapmaterial) is greater than an energy difference (e.g., a minimum energydifference) between the conduction band and the valence band in theinsulator/dielectric 84 (e.g., used to promote an electron from theconduction band to the valence band of the insulator/dielectric 84).Additionally, because the wide band gap material may include thematerial where an energy difference between the lowest unoccupiedelectronic levels (e.g., LUMO or lowest energy in the conduction band)and highest occupied electronic levels (e.g. HOMO or highest energy inthe valence band) is greater than that in the insulator/dielectric 84,the wide band gap material may also include a material where the lowestenergy in the conduction band or energy associated with the LUMO isgreater than the lowest energy in the conduction band of theinsulator/dielectric 84. In some embodiments, the wide band gap materialmay include a material where the band gap is 2 electronvolts (eV) andabove, 3 eV and above, 4 eV and above, 5 eV and above, and so on, suchas 4.4 eV and above. The wide band gap material may require more energyto promote (e.g., transfer) a valence electron into the conduction bandthan the energy to do so in the insulator/dielectric 84. Thus, the wideband gap material may act as an increased energy barrier for theconduction electrons.

Separating the semiconductive cathode 88 and the insulator/dielectric 84with a wide band gap material layer 86 may mitigate, reduce, or decreasethe anomalous charging current by blocking/reducing theinterface-limited conduction mechanisms (e.g., thermionic emission,thermionic-field emission, field emission, direct tunneling, and/orFowler-Nordhiem tunneling). That is, the wide band gap material layer 86at the cathode-dielectric interface 87 may increase an energy barrierthat electrons would need to overcome to move across the interface 87,reducing thermionic emission and field-thermionic emission across theinterface 87. Moreover, increased thickness of the non-conductive layers(including the insulator/dielectric 84 and the wide band gap materiallayer 86) and/or the increased energy barrier may reduce a probabilityof electrons tunneling through (e.g., field emission) by increasing thetunneling width. Additionally, the heightened energy barrier mayfacilitate restricting the bulk-limited current associated withPoole-Frenkel hopping by reducing or minimizing electron injection intoenergy “traps” inside a valence band of the dielectric 84.

As illustrated, the polymer capacitor 60A includes several layersdeposited/grown one on top of another. A conductive anode 82 of thepolymer capacitor 60A may be made of a metal or a material with metallicconductivity, such as tantalum (Ta), niobium (Nb), niobium monoxide(NbO), aluminum (Al), and so on. The insulator/dielectric 84 disposed onthe conductive anode 82 may include an electrical insulator, such astantalum pentoxide (Ta₂O₅), niobium pentoxide (Nb₂O₅), aluminum (III)oxide (Al₂O₃), and the like. The wide band gap material layer 86disposed on the insulator/dielectric 84 may be made of materials withthe electronic band gap higher than the electronic band gap of theinsulator/dielectric. The wide band gap material layer 86 may be made ofoxide, nitride, carbide, and/or polymer materials, including siliconnitride (Si₃N₄) (having a band gap of approximately 5.3 electronvolts(eV)), silicon dioxide (SiO₂) (having a band gap of approximately 9.0eV), zirconium dioxide (ZrO₂) (having a band gap of approximately 5.8eV), hafnium oxide (HfO₂) (having a band gap of approximately 5.8 eV),lanthanum(III) oxide (La₂O₃) (having a band gap of approximately 6.0eV), yttrium oxide (Y₂O₃) having a band gap of approximately 6.0 eV),polyethylene (having a band gap of approximately 6.9 eV), and/orpolypropylene (having a band gap of approximately 7.0 eV). Additionally,the semiconductive cathode 88 may be made of poly(3,4-ethylenedioxythiophene) (PEDOT), poly (3,4-ethylenedioxythiophene)and polystyrene sulfonate (PSS) slurry (PEDOT:PSS), or polypyrrole (PPy)may be disposed on the wide band gap material layer 86. Conductiveelectrodes 90 may be in contact with the conductive anode 82 and thesemiconductive cathode 88 of the polymer capacitor 60A.

FIG. 11 is a flowchart of a method 100 for producing the polymercapacitor 60A with a wide band gap material layer 86 between theinsulator/dielectric 84 and the semiconductive cathode 88, in accordancewith an embodiment of the present disclosure. The method 100 starts withforming the conductive anode 82 (block 102). As mentioned earlier, theconductive anode 82 may be made of a metal or a material with metallicconductivity, such as tantalum, niobium, niobium monoxide, and/oraluminum. Conductive anodes may come in various forms: a porous pellet,a film, or a foil. The porous pellet anode may have a higher volumetriccapacitance per unit of mass (due to higher surface area) than the filmor foil anodes and may be more commonly used in tantalum-based,niobium-based, and niobium monoxide-based polymer capacitors wherehigher charge density (which may be defined ascapacitance(C)*voltage(V)/gram(g)) is preferred. Production of pelletsfor use in capacitors may include pressing and compacting tantalum,niobium, or niobium monoxide powder into a pellet. The pressed pelletsthen undergo a sintering process where the pellets are heated in avacuum. Sintering allows pressed powder particles to stick together sothat they can hold an electrode wire. Film anodes are produced bydepositing anode material (e.g., Ta, Nb, NbO, Al) onto an inertsubstrate using physical or chemical deposition techniques (e.g.,physical vapor deposition, sputtering deposition, pulsed laserdeposition, chemical vapor deposition, and so on), as will be discussedlater. Foil anode is made of metal foil, and may be produced byhammering or rolling the metal (e.g., Al, Ta, Nb) to a desiredthickness. The foil to be used in anodes may be electrochemically etchedto increase its surface area.

An insulator/dielectric 84 is then deposited/grown on the conductiveanode 82 (block 104). The insulator/dielectric 84 may include an oxideof the metal found in the conductive anode 82, such as Ta₂O₅, Nb₂O₅, orAl₂O₃. For example, if the conductive anode 82 is made of tantalum, theinsulator/dielectric 84 may be made of Ta₂O₅. The insulator/dielectric84 may be deposited/grown on the conductive anode 82 using any suitableor variety of physical, chemical, and/or electrochemical depositiontechniques.

For example, one electrochemical deposition technique used to grow themetal oxide insulator/dielectric 84 of the polymer capacitors 60A iselectrochemical anodic oxidation (later referred to as electrochemicalanodization). Electrochemical anodization involves submerging twoterminals connected to a voltage source into an electrolyte solution(e.g., solution of weak acid), wherein a positive terminal is theconductive anode 82 of the polymer capacitor 60A. Applying a DC voltageto the terminals creates oxidation reactions at the positive terminalthat form a metal oxide film on the conductive anode 82. A totalthickness of the metal oxide film (e.g., the insulator/dielectric 84)may be determined by a voltage (e.g., a formation voltage) appliedduring the anodization process. Because the thickness of theinsulator/dielectric 84 may be proportional to the voltage rating of apolymer capacitor 60A, the voltage rating can be controlled by thevoltage applied during the anodization process. The voltage rating maybe the maximum amount of voltage that a polymer capacitor 60A can safelybe exposed to. The higher the voltage rating, the thicker theinsulator/dielectric layer 84 of the polymer capacitor 60A. For example,for a Ta₂O₅, Nb₂O₅, or Al₂O₃ capacitor, the thickness of the oxide filmassociated with a 1 Volt (V) voltage rating may be between 1 nanometers(nm) and 5 nm, 2 nm and 4 nm, or 1 nm and 3 nm, such as 1.4 nm and 2.5nm, depending upon the selected chemistry and process. As anotherexample, if the voltage range of interest is 1.5 V to 100 V, a formationvoltage may vary from 2.0 V to 300 V, which means the thickness of oxidefilm may be between 1 nm and 2000 nm, 2 nm and 1000 nm, or about 3 nmand 750 nm. Other advantages of electrochemical anodization are that itis a relatively inexpensive process, and that it enables easy additionof doping impurity into the metal oxide film. However, in somecircumstances, the electrochemical anodization may lead to a presence ofoxygen and/or metal vacancies in the metal oxide film, which couldresult in the bulk-limited current contribution to the abnormal chargingcurrent.

Another technique that may be used to deposit the insulator/dielectric84 is sputtering deposition. In particular, radio frequency (RF)sputtering is suitable for depositing metal oxide films. RF sputteringinvolves placing the target material (e.g., the insulator/dielectricmaterial 84 to be coated onto the conductive anode 82) and the substrate(e.g., the conductive anode 82 of the polymer capacitor 60A) in a vacuumchamber with ionized inert gas (e.g., Argon gas). The target material,which is given a negative charge, may be bombarded by high energy ionssputtering off atoms as a fine spray, which may cover the substrate. Analternating current (AC) that oscillates at a radio frequency (e.g.,13.56 MHz) is used to periodically alter the charge of the target,clearing it of a build-up of positive ions that would have preventedcontinued sputtering.

As illustrated, the wide band gap material layer 86 is deposited atopthe metal oxide film (block 108). In general, the wide band gap layer 86may be made of oxides, nitrides, carbides and/or polymer materials,where the energy difference between a lowest energy in the conductionband of the wide band gap layer 86 and a highest energy in the valenceband of the wide band gap layer 86 is higher than that of theinsulator/dielectric 84. Such materials may include Si₃N₄, SiO₂, ZrO₂,HfO₂, La₂O₃, Y₂O₃, polyethylene, and/or polypropylene. These materialsmay be deposited/grown using a variety of different methods includingsputtering, pulsed laser deposition (PLD), atomic layer deposition(ALD), metal organic chemical vapor deposition (MOCVD), electrochemicalanodization, other physical vapor deposition (PVD) methods, and/or otherchemical vapor deposition (CVD) methods. The deposition process may beselected based on a type of material used and/or a desired thickness ofthe layer, which may range from 1 picometer (pm) to 1 centimeter (cm),100 pm to 100 millimeters (mm), 0.1 nanometer (nm) to 1.0 mm, and so on.

PVD is a category of vacuum deposition methods where material transitionfrom a condensed phase to a vapor phase, and then back to a condensedphase depositing a thin film or a coating. Sputtering and PLD are twoexamples of PVD methods. As mentioned earlier, sputtering uses ionizedinert gas in a vacuum environment to eject atoms from a target (e.g., amaterial that is to be deposited) onto a substrate. PLD uses ahigh-power pulsed laser beam focused inside a vacuum chamber to strike atarget (e.g., material that is to be deposited) and create a plasmaplume that deposits the target material as a thin film onto thesubstrate.

CVD is a category of deposition methods where constituents in a vaporphase react to form a solid film/coating on a surface of a substrate.CVD is different from PVD in that it is a multidirectional type ofdeposition (e.g., able to coat a three-dimensional (3D) structure),whereas PVD is a line-of-site type of deposition (e.g., able to coat onesurface of a two-dimensional (2D) structure). Atomic layer deposition isa CVD method involving sequential reagent exposures and surface-limitedreactions to yield very thin films for precise control over coatingthickness and superior 3D surface coverage. Like ALD, MOCVD is also CVDtechnique for creating very thin coatings. However, it may result inepitaxial (e.g., highly ordered, mono- or polycrystalline) films. MOCVDinvolves combining various reactant gases at elevated temperaturescausing chemical reactions and resulting in the deposition of materialson the substrate. It is particularly useful in growing semiconductorfilms.

The semiconductive cathode 88 is then deposited on the wide band gapmaterial layer 86 (block 110). In particular, the polymer capacitor 60Amay be capped with the semiconductive cathode 88. For example, thesemiconductive cathode 88 may be made of PEDOT, PEDOT:PSS, and/or PPyconducting polymers. The semiconductive cathode 88 may be depositedusing chemical polymerization, electrochemical polymerization, PVD,and/or CVD methods. Moreover, PEDOT may be polymerized in-situ (e.g., onthe insulator/dielectric 84 or wide band gap material layer 86 of thepolymer capacitor 60A) by the oxidation of 3,4-ethylenedioxythiophene(EDOT) with catalytic compositions. PEDOT may also or alternatively bedeposited onto the polymer capacitor 60A as a pre-polymerized slurry,PEDOT:PSS. For polymer capacitors 60A having the conductive anode 82made of a porous pellet, a size of particles in the pre-polymerizedPEDOT:PSS slurries may be too large to penetrate into the porous pelletof the polymer capacitors 60A (e.g., a size of particles in the pelletis smaller than that of the size of the particles in the pre-polymerizedPEDOT:PSS slurries) and assure sufficient or full surface coverage ofthe insulator/dielectric 84. Therefore, to achieve certain desiredelectrical properties of the polymer capacitors 60A, PEDOT may be firstpolymerized in-situ, and then deposited as pre-polymerized PEDOT:PSSslurry. However, in certain other cases (e.g., in which the conductiveanode 82 is not made of the porous pellet or where the size of theparticles in the porous pellet is large), having only pre-polymerizedPEDOT:PSS or only in-situ polymerized PEDOT may be advantageous. WhenPPy is used in the semiconductive cathode 88, PPy may be polymerizedin-situ through the oxidative polymerization of pyrrole. Additionally oralternatively, PPy can also be formed in-situ using electrochemicalpolymerization.

An additional or alternative embodiment that may mitigate, reduce, ordecrease the anomalous charging current phenomenon has a chargedepletion region inside the insulator/dielectric 84. FIG. 12 is aperspective diagram of a polymer capacitor 60B with a charge depletionregion 89 in the insulator/dielectric 84, in accordance with anembodiment of the present disclosure. The polymer capacitor 60B includesa conductive anode 82 made of a metal or a metallic material (e.g., Ta,Nb, NbO, or Al). An insulator/dielectric 84 (e.g., Ta₂O₅, Nb₂O₅, Al₂O₃)may be in contact with or adjacent to the conductive anode 82. Theinsulator/dielectric 84 has a charge depletion region 89 having a chargedonor (e.g., n-type or negative type) doping impurity 92. In someembodiments, the charge depletion region 89 may also include a chargeacceptor (e.g., p-type or positive type) doping impurity 94. The chargeacceptor doping impurity 94 may be made from an element or a compoundfrom Group 13 in the periodic table, such as boron (B) or gallium (Ga).In addition, the charge donor doping impurity 92 may be made from anelement or a compound from Group 15 in the periodic table, such asphosphorus (P), arsenic (As) or antimony (Sb). The n-type and p-typedoping impurities 92 and 94 may form a p-n junction and the chargedepletion region 89, which may reduce a number of, or altogetherprevent, charge carriers from passing through. Thus, the resultingcharge depletion region 89 may mitigate the bulk-limited currentassociated with oxygen and metal vacancies as voltage quickly increases.The polymer capacitor 60B may also have semiconductive cathode 88 andconductive electrodes 90.

Now, we turn to the method of production of the polymer capacitor 60Bwith a charge depletion region 89 in the insulator/dielectric 84. FIG.13 is a flowchart of a method 120 for producing the polymer capacitor60B with the charge depletion region 89 in the insulator/dielectric 84,in accordance with an embodiment of the present disclosure. The firststep in the production method 120 is to form the conductive anode 82 ofthe polymer capacitor 60B (block 102, as discussed in more detail abovewith respect to the method 100 of FIG. 11 ). As mentioned earlier, theconductive anode 82 may be made of a porous pellet (e.g., a pressed andsintered pellet of Ta, Nb, or NbO powder), a film (e.g., a film of Ta,Nb, NbO, or Al), or a foil (e.g., etched foil of Ta, Nb or Al).

An insulator/dielectric 84 with a charge depletion region 89 isdeposited over the conductive anode 82 (block 106). Depositing theinsulator/dielectric 84 with a charge depletion region 89 may include amultistep process. First, a layer of insulator/dielectric 84 (e.g.,Ta₂O₅, Nb₂O₅, Al₂O₃) is deposited/grown over the conductive anode 82.Next, an n-type (electron donor) doping impurity 92 made of an elementfrom Group 15 of the periodic table (e.g., P, As, Sb) may be introduced.A layer of undoped insulator/dielectric 84 may then be added, followedby a p-type impurity made of an element from Group 13 of the periodictable (e.g., P, As, or Sb). The insulator/dielectric 84 with the chargedepletion region 89 may be completed by growing the undopedinsulator/dielectric 84 (e.g., Ta₂O₅, Nb₂O₅, Al₂O₃) to a final thicknessof the layer.

The doping impurities 92 and 94 may be introduced using electrochemicalanodization, vapor phase epitaxy, PVD, ion diffusion and ionimplantation. The metal oxide or insulator/dielectric 84 may be dopedusing electrochemical anodization by adding the impurity element orcompound (e.g., B, Ga, P, As, Sb) to the electrolyte solution thatoxidizes the conductive anode 82. Vapor phase epitaxy (such as MOCVD)involves combining various reactant gases and metaloranic precursors toproduce chemical reactions that form crystals of the impurity element orcompound (e.g., B, Ga, P, As, Sb). Ion diffusion (e.g., gas phase,liquid phase, or solid phase diffusion) may carry the doping elements orcompounds (e.g., B, Ga, P, As, Sb) from a region of higher concentrationto one of lower concentration. To add an impurity using ionimplantation, charged dopants (e.g., B, Ga, P, As, Sb) may beaccelerated in an electric field and irradiated onto the substrate(e.g., the insulator/dielectric 84 of the polymer capacitor 60B). Apenetration depth of the impurity into the substrate can be set byvarying a voltage needed to accelerate the ions.

The semiconductive cathode 88 is then deposited on theinsulator/dielectric 84 (block 110, as discussed in more detail abovewith respect to the method 100 of FIG. 11 ). In particular, the polymercapacitor 60B is capped with the semiconductive cathode 88. As mentionedearlier, the semiconductive cathode 88 may be made of PEDOT or PPyconducting polymers. Moreover, PEDOT may be polymerized in-situ and/orbe deposited as or in combination with pre-polymerized PEDOT:PSS slurry.PPy is an alternative to PEDOT that is typically chemically orelectrochemically polymerized in-situ. The conducting polymers may bedeposited as the semiconductive cathode 88 using chemicalpolymerization, electrochemical polymerization, PVD, and/or CVD methods.

In some embodiments, the two polymer capacitors 60A, and 60B describedabove may be combined to into a single polymer capacitor 60C that hasboth a wide band gap material layer 86 between the insulator/dielectric84 and the semiconductive cathode 88 and a charge depletion region 89 inthe insulator/dielectric 84. FIG. 14 is a perspective diagram of thepolymer capacitor 60C, in accordance with an embodiment of the presentdisclosure. The polymer capacitor 60C may have a conductive anode 82made of a metal or a metallic material (e.g., Ta, Nb, NbO, Al), and aninsulator/dielectric 84 (e.g., Ta₂O₅, Nb₂O₅, Al₂O₃) with a chargedepletion region 89 having an n-type doping impurity 92 and a p-typedoping impurity 94. As mentioned earlier, the charge depletion region 89may mitigate the bulk-limited current associated with oxygen and metalvacancies by preventing charge carriers from passing through it. Anelement or a compound from Group 13 in the periodic table (e.g., B orGa) may be used to create a p-type doping impurity 94, and an element ora compound from Group 15 in the periodic table (e.g., P, As, Sb) may beused to create an n-type doping impurity 92. The wide band gap materiallayer 86 disposed on the insulator/dielectric 84 may be made of oxide,nitride, carbide, polymer, or any other suitable materials that have anelectronic band gap wider that of the insulator/dielectric 84. The wideband gap material layer may include Si₃N₄, SiO₂, ZrO₂, HfO₂, La₂O₃,Y₂O₃, polyethylene, and/or polypropylene. A semiconductive cathode 88may be in contact with or adjacent to the insulator/dielectric 84 havingthe charge depletion region 89. In addition, conductive electrodes 90are in contact with the conductive anode 82 and the semiconductivecathode 88.

FIG. 15 is a flowchart of a method 130 for producing the polymercapacitor 60C with the charge depletion region 89 in theinsulator/dielectric 84, in accordance with an embodiment of the presentdisclosure. The first step in the production process 130 is to form theconductive anode 82 of the polymer capacitor 60C (block 102, asdiscussed in more detail above with respect to the method 100 of FIG. 11). As mentioned earlier, the conductive anode 82 may be made of apressed pellet (e.g., a sintered pellet of Ta, Nb, or NbO powder), afilm (e.g., a film of Ta, Nb, NbO, or Al), or a foil (e.g., etched foilof Ta, Nb, or Al).

An insulator/dielectric 84 with a charge depletion region 89 is thendeposited over the conductive anode 82 (block 106, as discussed in moredetail above with respect to the method 100 of FIG. 13 ). Depositing theinsulator/dielectric 84 with the charge depletion region 89 may includea multistep procedure. First, a layer of insulator/dielectric 84 (e.g.,Ta₂O₅, Nb₂O₅, Al₂O₃) is deposited/grown. As discussed earlier, this maybe accomplished using a variety of different deposition processes, suchas PVD, PLD, sputtering, CVD, ALD, MOCVD, and/or electrochemicalanodization, among others. Next, an n-type (electron donor) dopingimpurity 92 made of an element from Group 15 of the periodic table(e.g., P, As, Sb) is introduced. A layer of undoped insulator/dielectric84 may then be added, followed by a p-type impurity made of an elementfrom Group 13 of the periodic table (e.g., B, Ga). Both electron donor(n-type) and electron acceptor (p-type) doping impurities 92 and 94 maybe introduced using electrochemical anodization, vapor phase epitaxy,PVD, ion diffusion, and/or ion implantation. The insulator/dielectric 84with the charge depletion region 89 may be completed by growing theundoped insulator/dielectric 84 (e.g., Ta2O5, Nb2O5, Al2O3) to a totalthickness equivalent to a desired voltage rating. In some embodiments,the voltage rating of the polymer capacitor 60C (as well as polymercapacitors 60A and 60B) may range from 1.5 V to 100 V, from 5 V to 80 V,and from 10 V to 50 V, and so on. In some embodiments, the thickness ofthe insulator/dielectric 84 corresponding to the voltage rating of thepolymer capacitor 60C (as well as polymer capacitors 60A and 60B) mayrange from 3 nm to 750 nm, from 10 nm to 600 nm, and from 50 nm to 400nm, and so on.

The insulator/dielectric 84 with the charge depletion region 89 may thenbe topped with the wide band gap material layer 86 (block 108, asdiscussed in more detail above with respect to the method 100 of FIG. 11). As mentioned above, the wide band gap layer 86 may be made of metaloxides, nitrides, carbides, and/or polymer materials with an electronicband gap wider than the electronic band gap of the insulator/dielectric84. The wide band gap layer may include Si₃N₄, SiO₂, ZrO₂, HfO₂, La₂O₃,Y₂O₃, polyethylene, and/or polypropylene. These materials may bedeposited/grown using any suitable or variety of methods, includingsputtering, pulsed laser deposition (PLD), atomic layer deposition(ALD), metal organic chemical vapor deposition (MOCVD), electrochemicalanodization, other physical vapor deposition (PVD), and/or chemicalvapor deposition (CVD) methods. The appropriate deposition process maydepend on the type of material used as well as the desired thickness ofthe layer, which may range from 1 picometer (pm) to 1 centimeter (cm),100 pm to 100 millimeters (mm), 0.1 nanometer (nm) to 1.0 mm, and so on.

The polymer capacitor 60C may then be capped with a semiconductivecathode 88 (block 110, as discussed in more detail above with respect tothe method 100 of FIG. 11 ). As mentioned earlier, the semiconductivecathode 88 may include PEDOT and/or PPy conducting polymers. Moreover,PEDOT may be polymerized in-situ and/or be deposited as or incombination with a pre-polymerized PEDOT:PSS slurry. Additionally oralternatively, PPy may be chemically or electrochemically polymerizedin-situ. The conducting polymers may be deposited as a semiconductivecathode 88 using chemical polymerization, electrochemicalpolymerization, PVD, and/or CVD methods.

Three different polymer capacitors for mitigating the anomalous chargingcurrent have been presented: a polymer capacitor 60A with a wide bandgap material layer 86; a polymer capacitor 60B with a charge depletionregion 89 in the insulator/dielectric 84; and a polymer capacitor 60Cwith both a wide band gap material layer 86 and a charge depletionregion 89 in the insulator/dielectric 84. General methods 100, 120, 130for producing each polymer capacitor 60A, 60B, 60C have also beendescribed. Specific production methods for the three polymer capacitors60A, 60B, 60C follow.

One specific embodiment of the polymer capacitor 60A with a wide bandgap material layer 86 may include a tantalum-based polymer capacitorwith a wide band gap SiO₂ layer. FIG. 16 is a flowchart of a method 100Afor producing such a tantalum-based polymer capacitor, in accordancewith an embodiment of the present disclosure. The method 100A includesforming a tantalum (Ta) pellet used as the conductive anode 82 (block102A). Next, Ta₂O₅ insulator/dielectric 84 may be grown over Ta in amultistep process (e.g., a specific example of block 104 as discussedabove with respect to method 100 of FIG. 11 ). In particular, Ta₂O₅ isgrown over Ta using an electrochemical deposition (e.g., electrochemicalanodization) (block 104A). Then, a thermal treatment is performed (block104B), which involves heating and cooling the polymer capacitor 60A atto a desired temperature. The thermal treatment (block 104B) may arrangethe atoms of Ta₂O₅ insulator/dielectric 84 in a configuration that ismore stable under an applied electric field, thus decreasing thebulk-limited conduction within the insulator/dielectric 84. In addition,the thermal treatment (block 104B) may increase the relativepermittivity of the insulator/dielectric 84 by modifying its crystallineproperties and morphology. The insulator/dielectric 84 may then undergoplasma cleaning in order to remove impurities and contaminants from theelectrochemically grown Ta₂O₅ (block 104C). After the Ta₂O₅ formation iscompleted, a wide band gap material layer 86 made of SiO₂ is depositedusing a physical vapor deposition method (e.g., sputtering, pulsed laserdeposition, or the like) (block 108A), followed by thermal treatment(block 108B, similar to that of 104B described above). The thermaltreatment may improve the crystalline characteristics of the SiO₂ wideband gap layer 86. The semiconductive cathode 88 made of PEDOT may thenbe deposited (as generally described above with respect to block 110 ofmethod 100 in FIG. 11 ). In particular, PEDOT is polymerized in-situ(block 110A), followed by deposition of pre-polymerized PEDOT:PSS slurry(block 110B).

A specific embodiment of a polymer capacitor 60B with a charge depletionregion 89 in the insulator/dielectric 84 is a tantalum-based capacitorwith a charge depletion region 89 formed from phosphorus (P) and boron(B) impurities in the insulator/dielectric 84. FIG. 17 is a flowchart ofa method 120A for producing such a tantalum-based polymer capacitor, inaccordance with an embodiment of the present disclosure. The method 120Aincludes forming a tantalum (Ta) pellet used as the conductive anode 82(block 102A). Next, Ta₂O₅ insulator/dielectric 84 is grown over Ta in amultistep process (e.g., a specific example of block 106 as discussedabove with respect to method 120 of FIG. 13 ). In particular, Ta₂O₅ isgrown over Ta in a phosphoric acid-based solution using electrochemicaldeposition (e.g., electrochemical anodization), and the phosphorusimpurity 92 is introduced (block 106A). Then, a thermal treatment isperformed (block 106B). The thermal treatment (block 106B) may arrangethe atoms of the doped Ta₂O₅ insulator/dielectric 84 in a configurationthat is more stable under an applied electric field, thus decreasing thebulk-limited conduction within the insulator/dielectric 84. In addition,the thermal treatment (block 106B) may improve crystalline propertiesand morphology of the insulator/dielectric 84 with the charge depletionregion 89, increasing the relative permittivity of theinsulator/dielectric 84. Ta₂O₅ growth is continued in a boric acid-basedsolution using electrochemical deposition, and the boron impurity 94 isintroduced (block 106C). The electrochemical deposition is followed byanother thermal treatment (block 106B). The semiconductive cathode 88made of PEDOT polymerized in-situ is then formed (block 110A, asgenerally described above with respect to block 110 of method 120 inFIG. 13 )

FIG. 18 presents another method 120B for producing a tantalum-basedpolymer capacitor 60B with a charge depletion region 89 formed fromphosphorus (P) and boron (B) impurities in the insulator/dielectric 84.FIG. 18 is a flowchart of a method 120B for producing such atantalum-based polymer capacitor, in accordance with an embodiment. Themethod 120B includes forming a tantalum (Ta) pellet used as theconductive anode 82 (block 102A). Next, Ta₂O₅ insulator/dielectric 84may be grown over Ta in a multistep process (e.g., a specific example ofblock 106 as discussed above with respect to method 120 of FIG. 13 ). Inparticular, Ta₂O₅ is deposited over Ta using sputtering (block 106D).The phosphorus impurity 92 is then added using ion implantation (block106E) followed by a thermal treatment (block 106B). Next, a thin layerof pure Ta₂O₅ is added using ion implantation (block 106F). Ta₂O₅ growthis continued in a boric acid-based solution using electrochemicaldeposition (e.g., electrochemical anodization), and a boron impurity 94is introduced (block 106C). The electrochemical deposition is followedby another thermal treatment (block 106B). The semiconductive cathode 88made of PEDOT may then be deposited (as generally described above withrespect to block 110 of method 120 in FIG. 13 ). In particular, PEDOT ispolymerized in-situ (block 110A), followed by deposition ofpre-polymerized PEDOT:PSS slurry (block 110B).

A specific embodiment of a polymer capacitor 60C with a charge depletionregion 89 in the insulator/dielectric 84 and a wide band gap materiallayer 86 may include a tantalum-based capacitor with a charge depletionregion 89 formed from phosphorus (P) and boron (B) impurities in theinsulator/dielectric 84, and a wide band gap La₂O₃ layer 86. FIG. 19 isa flowchart of a method 130A for producing such a tantalum-based polymercapacitor, in accordance with an embodiment of the present disclosure.The method 130A includes forming a tantalum (Ta) pellet used as theconductive anode 82 (block 102A). Next, Ta₂O₅ insulator/dielectric 84 isgrown over Ta in a multistep process (e.g., a specific example of block106 as discussed above with respect to method 130 of FIG. 15 ). Inparticular, Ta₂O₅ is deposited over Ta using sputtering (block 106D).The phosphorus impurity 92 is then added using ion implantation (block106E) followed by a thermal treatment (block 106B). Next, a thin layerof pure Ta₂O₅ is added using ion implantation (block 106F). Ta₂O₅ growthis continued in a boric acid-based solution using electrochemicaldeposition (e.g., electrochemical anodization), and a boron impurity 94is introduced (block 106C). The electrochemical deposition is followedby another thermal treatment (block 106B). After the Ta₂O₅ formation iscompleted, a wide band gap material layer 86 made of La₂O₃ is depositedusing atomic layer deposition (block 108C) The semiconductive cathode 88made of PEDOT may then be deposited (as generally described above withrespect to block 110 of method 130 in FIG. 15 ). In particular, PEDOT ispolymerized in-situ (block 110A), followed by deposition ofpre-polymerized PEDOT:PSS slurry (block 110B).

FIG. 20 is a flowchart of a method 130B for producing a niobiummonoxide-based polymer capacitor (a specific embodiment of a polymercapacitor 60C) with charge depletion region 89 formed from phosphorus(P) and boron (B) impurities in the insulator/dielectric 84 and a wideband gap HfO₂ layer 86, in accordance with an embodiment. The method130B includes using a niobium monoxide (NbO) pellet as the conductiveanode 82 (block 102B). Next, Nb₂O₅ insulator/dielectric 84 is grown overNbO in a multistep process (e.g., a specific example of block 106 asdiscussed above with respect to method 130 of FIG. 15 ). In particular,Nb₂O₅ is deposited over NbO using electrochemical deposition (e.g.,electrochemical anodization) (block 106G). The phosphorus impurity 92 isthen added using ion implantation (block 106H) followed by a thermaltreatment (block 106B). Nb₂O₅ growth is continued in a boric acid-basedsolution using electrochemical deposition and a boron impurity 94 isintroduced (block 106I). The electrochemical deposition is followed by athermal treatment (block 106B). After the Nb₂O₅ formation is completed,a wide band gap material layer 86 made of HfO₂ is deposited usingchemical vapor deposition (e.g., ALD, MOCVD, or the like) (block 108D).The semiconductive cathode 88 made of PEDOT may then be deposited (asgenerally described above with respect to block 110 of method 130 inFIG. 15 ). In particular, PEDOT is polymerized in-situ (block 110A),followed by deposition of pre-polymerized PEDOT:PSS slurry (block 110B).

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The specific embodiments described above have been shown by way ofexample, and it should be understood that these embodiments may besusceptible to various modifications and alternative forms. It should befurther understood that the claims are not intended to be limited to theparticular forms disclosed, but rather to cover all modifications,equivalents, and alternatives falling within the spirit and scope ofthis disclosure.

The techniques presented and claimed herein are referenced and appliedto material objects and concrete examples of a practical nature thatdemonstrably improve the present technical field and, as such, are notabstract, intangible or purely theoretical. Further, if any claimsappended to the end of this specification contain one or more elementsdesignated as “means for [perform]ing [a function]...” or “step for[perform]ing [a function]...” it is intended that such elements are tobe interpreted under 35 U.S.C. 112(f). However, for any claimscontaining elements designated in any other manner, it is intended thatsuch elements are not to be interpreted under 35 U.S.C. 112(f).

1. A capacitor, comprising: a conductive anode; a dielectric layerdisposed on the conductive anode; a wide band gap layer disposed on thedielectric layer; a semiconductive cathode disposed on the wide band gaplayer; an electron acceptor doping impurity of a charge depletion regionof the dielectric layer; an electron donor doping impurity of the chargedepletion region; and an undoped portion of the dielectric layerdisposed between the electron acceptor doping impurity and the electrondonor doping impurity.
 2. The capacitor of claim 1, wherein: theconductive anode comprises tantalum (Ta), niobium (Nb), aluminum (Al),or niobium monoxide (NbO), or any combination thereof; and thedielectric layer comprises tantalum pentoxide (Ta2O5), niobium pentoxide(Nb2O5), or aluminum(III) oxide (Al2O3), or any combination thereof. 3.The capacitor of claim 1, wherein the electron donor doping impurity isdisposed between the electron acceptor doping impurity and theconductive anode.
 4. The capacitor of claim 1, wherein an energydifference between a lowest energy in a conduction band of the wide bandgap layer and a highest energy in a valence band of the wide band gaplayer is greater than an energy difference between a lowest energy in aconduction band of the dielectric layer and a highest energy in avalence band of the dielectric layer.
 5. The capacitor of claim 1,wherein an amount of energy used to promote an electron from a highestoccupied molecular orbital in the wide band gap layer to a lowestunoccupied molecular orbital in the wide band gap layer is greater thanan amount of energy used to promote an electron from a highest energy ina valence band in the dielectric layer to a lowest energy in aconduction band in the dielectric layer.
 6. The capacitor of claim 1,wherein the wide band gap layer comprises silicon nitride (Si3N4),silicon dioxide (SiO2), zirconium dioxide (ZrO2), hafnium oxide (HfO2),lanthanum(III) oxide (La2O3), yttrium oxide (Y2O3), polyethylene, orpolypropylene, or any combination thereof.
 7. The capacitor of claim 1,wherein the semiconductive cathode comprises poly(3,4-ethylenedioxythiophene) (PEDOT), poly (3,4-ethylenedioxythiophene)polystyrene sulfonate (PEDOT:PSS), or polypyrrole (PPy), or anycombination thereof.
 8. A capacitor comprising: a conductive anode; aninsulator layer disposed on the conductive anode, the insulator layerhaving a charge depletion region formed therein; an electron acceptordoping impurity of the charge depletion region; an electron donor dopingimpurity of the charge depletion region, wherein the electron donordoping impurity is disposed between the electron acceptor dopingimpurity and the conductive anode; and a semiconductive cathode disposedon the insulator layer.
 9. The capacitor of claim 8, wherein theelectron donor doping impurity comprises phosphorus (P), arsenic (As),or antimony (Sb), or any combination thereof.
 10. The capacitor of claim8, wherein the electron acceptor doping impurity comprises boron (B), orgallium (Ga), or both.
 11. The capacitor of claim 8, wherein thesemiconductive cathode is comprised of a semiconductive polymer, and theconductive anode is comprised of a conductive material.
 12. Thecapacitor of claim 8, wherein the insulator layer is comprised of anoxide of a conductive material found in the conductive anode. 13.(canceled)
 14. The capacitor of claim 8, wherein: the electron donordoping impurity comprises elements or compounds from Group 15 of aperiodic table of elements; and the electron acceptor doping impuritycomprises elements or compounds from Group 13 of the periodic table ofelements.
 15. A capacitor, comprising: a conductive anode; a dielectriclayer formed on the conductive anode, the dielectric layer having acharge depletion region formed therein; an electron acceptor dopingimpurity of the charge depletion region; an electron donor dopingimpurity of the charge depletion region, wherein the electron donordoping impurity is disposed between the electron acceptor dopingimpurity and the conductive anode; a wide band gap layer deposited onthe dielectric layer and configured to decrease an anomalous chargingcurrent in the capacitor; and a semiconductive cathode.
 16. Thecapacitor of claim 15, wherein an energy difference between a lowestenergy in a conduction band of the wide band gap layer and a highestenergy in a valence band of the wide band gap layer is greater than anenergy difference between a lowest energy in a conduction band of thedielectric layer and a highest energy in a valence band of thedielectric layer.
 17. The capacitor of claim 15, wherein an amount ofenergy used to promote an electron from a highest occupied molecularorbital in the wide band gap layer to a lowest unoccupied molecularorbital in the wide band gap layer is greater than an amount of energyused to promote an electron from a highest energy in a valence band inthe dielectric layer to a lowest energy in a conduction band in thedielectric layer.
 18. The capacitor of claim 15, wherein: the electrondonor doping impurity comprises elements or compounds from Group 15 of aperiodic table of elements; and the electron acceptor doping impuritycomprises elements or compounds from Group 13 of the periodic table ofelements.
 19. The capacitor of claim 15, wherein the charge depletionregion is configured to decrease the anomalous charging current in thecapacitor by reducing a bulk-limited current within the dielectric layerassociated with oxygen and metal vacancies.
 20. The capacitor of claim15, wherein the wide band gap layer is configured to decrease theanomalous charging current in the capacitor by increasing an energybarrier between the semiconductive cathode and the dielectric layer. 21.(canceled)
 22. A capacitor, comprising: a conductive anode; a dielectriclayer disposed on the conductive anode; a wide band gap layer disposedon the dielectric layer; a semiconductive cathode disposed on the wideband gap layer; an electron acceptor doping impurity of a chargedepletion region of the dielectric layer; and an electron donor dopingimpurity of the charge depletion region, wherein the electron donordoping impurity is disposed between the electron acceptor dopingimpurity and the conductive anode.